The present invention relates to a surveying system, in particular, to a surveying system using a surveying instrument with a tracking function.
As a surveying instrument for measuring a distance, a horizontal angle and a vertical angle, a surveying instrument provided with the tracking function has been known in the past. In this type of the surveying instrument, an object reflector (target) such as a corner cube is collimated by a collimating telescope provided on the surveying instrument. A tracking light is projected from the collimating telescope, and when the target is moved, a reflection light from the target is received and the target can be automatically tracked.
Normally, in a surveying instrument with the tracking function, no operator is assigned on the surveying instrument side, and a surveying operator works on the target side. The target is supported by the surveying operator or the target is supported on a construction machine and is moved.
In a case a moving speed of the target exceeds a following speed of the surveying instrument and the target goes out of a visual field of the collimating telescope or in case an obstacle such as a tree, a vehicle, a person, etc. temporarily comes into a space between the surveying instrument and the target, and the obstacle intercepts an optical path of the collimating telescope, the surveying instrument cannot receive a reflected light from the target, and an automatic tracking may be interrupted.
The reason for this is that, in a collimating telescope generally in use, a field angle (an angle of view) is as small as about 1° and a range to detect the reflection light for purpose of the automatic tracking is too narrow.
When the automatic tracking of the target is interrupted, the surveying instrument starts an operation to search the target. In the searching operation, the collimating telescope is rotated within a predetermined range in up-to-bottom direction and in left-to-right direction while the tracking light is projected for scanning and the target is detected.
In a conventional searching method, a scanning is performed by changing an elevation angle within a range of a predetermined horizontal angle using a position detected lastly by the collimating telescope on the surveying instrument side as a reference (FIG. 6 (A)), or the scanning or the like is carried out in a spiral manner from the last detected position (FIG. 6 (B)), and the target 12, which has been missed out of sight, is detected.
As described above, the field angle of the collimating telescope is small, in order to re-detect the target, it is necessary to have a finer scanning pitch. For this reason, when the automatic tracking is interrupted, much time is required for the purpose of detecting the target again and starting the automatic tracking operation. Further, under working conditions where the optical path is frequently intercepted by the obstacle, there is a problem in that a working efficiency of the measuring operation is extremely decreased.
A surveying instrument, which has the tracking function and performs searching when the tracking operation is interrupted, is disclosed in JP-A-2004-132914.